The present invention relates to a method of formulating alkali earth salts and more particularly, the present invention relates to a method of gene rating food grade sodium bicarbonate and fertilizer grade potassium sulfate.
A significant amount of prior art has been promulgated with respect to the formulation of alkali earth salts. Sodium bicarbonate, as an example, has been prepared in as many different ways as it has been known. Despite this fact, previous unit operations for bicarbonate synthesis have been hampered by inefficient energy use which results directly in increased synthesis costs. As a further limitation, known processes do not make efficient use of the unit operations involved in the preparation of salts. Typically, a single high quality product is formulated with concomitant byproduct formation of a quality inadequate for commercial purposes or that would require too substantial an investment to render them commercially viable.
Representative of the prior art is U.S. Pat. No. 3,429,657, issued Feb. 25, 1969, to D""Arcy. The reference discusses a method for recovering and producing potassium salts. In the reference, a potassium bearing brine is reacted with sodium perchlorate to precipitate potassium perchlorate. The potassium is removed by ion exchange with sodium and the free potassium is then combined with chloride, sulfate, nitrate inter alia.
One object of the present invention is to provide a method of formulating food grade sodium bicarbonate and potassium sulfate, comprising the steps of:
a) providing a source of liquid sodium sulfate;
b) providing a source of ammonium bicarbonate;
c) contacting the sodium sulfate and the ammonium bicarbonate;
d) precipitating sodium bicarbonate and forming a liquor;
e) precipitating sodium bicarbonate and forming a liquor by contacting the liquor from step d) with sodium sulfate;
f) saturating the liquor from step e) with sodium sulfate;
g) filtering solids from the liquor of step f);
h) contacting the liquor from step g) with sulfuric acid to precipitate carbonates;
i) cooling the liquor from step h) to 0xc2x0 C. to form Glauber""s salt precipitate;
j) heating the liquor from step i) to between 30xc2x0 to 40xc2x0 C.; and
k) precipitating potassium sulfate by contacting the liquor from step j) with potassium chloride.
A further object of the present invention is to provide a method of formulating food grade sodium bicarbonate and potassium sulfate, comprising the steps of:
a) providing a source of liquid sodium sulfate;
b) providing a source of ammonium bicarbonate;
c) contacting the sodium sulfate and the ammonium bicarbonate;
d) precipitating sodium bicarbonate and forming a liquor;
e) precipitating sodium bicarbonate and forming a liquor by contacting the liquor from step e) with sodium sulfate;
f) saturating the liquor from step e) with anhydrous sodium sulfate;
g) filtering solids from the liquor of step f);
h) contacting the liquor from step g) with at least one of ammonium bicarbonate, ammonia gas or carbon dioxide to precipitate sodium bicarbonate;
i) cooling the liquor from step h) to 0xc2x0 C. to a precipitate of sodium bicarbonate and sodium sulfate; and
j) precipitating potassium sulfate by contacting the liquor from step i) with potassium chloride.
It has been found that following the sodium bicarbonate formulation, significant success in cooling the liquor to 0xc2x0 C. is realized for removing sodium sulfate as Glauber""s salt and sodium bicarbonate. Glauber""s salt solubility in the system is contemplated by the ammonium sulfate-sodium sulfate phase diagram. By increasing the sodium sulfate in the bicarbonate circuit with increased Glauber""s salt recycle, there is a tendency to decrease the bicarbonate solubility and increase the process efficiency.
Regarding the conversion of the starting reagents to potassium sulfate, particular success has been encountered by maintaining a mole ratio of five (5) or greater for the potassium and ammonium ions. This ratio ensures high conversion efficiency in the second stage of the process.
Having thus described the invention, reference will now be made to the accompanying drawings illustrating preferred embodiments.